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By J. P. Ibáñez

The uptake of copper from extremely dilute aqueous solutions by alginate in the form of protonated dry alginate beads was investigated. Barium was used to cross link the alginate forming the beads. The effect of various experimental parameters such as pH and metal ions concentration on the uptake of copper were studied. The uptake was strongly dependent on the Cu-bearing solution pH up to a value of 4.5. A removal of 100% o was achieved when the initial concentration of copper was as low as 8.0 mg/L. The maximum uptake, i, e., the loading capacity, was found to be 167 mg of copper per g of beads. The mechanism governing the removal of copper was found to be ion exchange between protons of the alginate beads and cupric ions of the solution. For this ion exchange process a molar ratio, d[H+]/d[Cu2+], of 2.0 was determined. EPMA-EDX analysis of the Cu-loaded beads showed a uniform distribution of the ions throughout the structure of the alginate, regardless the solution pH. This may suggest that this sorbent material is a porous ion exchanger having high permeability and capacity. The uptake of copper and of the heavy metals cadmium and zinc by this sorbent is compared.

Jan 1, 1999

By Arpad E. Tonna

Recycling of materials from lithium-oxyhalide batteries is a complex task, since the dismantling of batteries is associated with many hazards. The electrolyte and the lithium anode metal are extremely reactive in the presence of water or water vapor. Therefore, the dismantling process is a complex task. In this process, the lithium battery is electrically discharged, then frozen in liquid argon, and cut into small size pieces. These are fed into an incinerator, where the unreacted portion of lithium metal, thionyl chloride, plastic separators and carbon paste are decomposed and burned to gaseous products. The aluminum, iron (steel) and nickel pieces are recovered as saleable scrap metals. The off-gases are scrubbed with an alkaline sodium carbonate containing solution. The clean gases are released to the environment. The particulate mater recovered from the scrub-suspension would be available as additive to the cement industry . The recycling of battery decomposition products improves the economic viability of the disposal processes. Work is in progress to develop safe handling, processing and recycling large size lithium batteries.

Jan 1, 1995

By Paul S. Korinko, Simona E. Hunyadi Murph

To address a radiological contamination event, a materials and process project was initiated. During the course of this project, processes and materials were developed that successfully captured zinc vapors physically and chemically, respectively. However, the physical traps were placed in an undesirable area and it was determined that the chemically captured zinc reactions was reversible. Consequently, advanced nanomaterials are being developed to capture zinc vapors. The current state of the art of the science and engineering of these materials and their efficacy for zinc capture and retention is discussed in this paper.

Jan 1, 2015

By Kafui Nyavor

Acid mine drainage (AMD) is presently the biggest single environmental problem facing the mining industry. New and expanding metal mines in most parts of the world have to demonstrate their ability to contain this problem to obtain operating permits. Conventional methods of controlling acid mine drainage have primarily been limited to collecting the drainage and neutralizing with alkaline materials which do not provide a permanent solution to the AMD problem. Since acid mine drainage results from the oxidation of sulfides in the presence of oxygen, water and iron-oxidizing bacteria, controlling any of these three factors contributing to pyrite oxidation provides a potential at-source remedy for reducing or preventing acid mine drainage formation. Physical properties such as hydrophobicity also play an important role in the attachment of bacteria, adsorption of oxygen, water, and other ions that subsequently lead to the oxidation of pyrite. In this communication, the suppression of pyrite oxidation by treatment with fatty acid amines (FAA) was investigated. The FAA treated pyrite samples were tested at various conditions of temperature and pressure. At an elevated oxygen pressure of 500 psi and a temperature of 600 C, less than 0.2% oxidation was obtained for the FAA treated pyrite samples, while over 1.2% oxidation was obtained for the untreated samples in 10 hours of oxidation time. Accelerated column oxidation tests at ambient condition showed that FAA mated samples reduced pyrite oxidation by at least 75% in 81 days.

Jan 1, 1994

By Houyuan Liu

A new process was developed to recover nickel and cobalt by leaching laterite ore at atmospheric pressure and.95"-105" C. The nickel-containing goethite in limonite was first leached with sulphuric acid to liberate over 90% of nickel, cobalt and iron. The dissolved iron was then precipitated as Ni-free goethite by the additioil of saprolite. The acid released during iron precipitation as goethite was simultaneously used as lixiviant to leach saprolite to recover more nickel. With this process the limonite and saprolite were essentially converted into goethite-, gypsum- and silica- containing tailings. Twenty bench scale tests and two campaigns of pilot plant operation were carried out at BHP Billiton's Newcastle Technology Centre (NTC) from January to August 2002. The overall nickel and cobalt extractions were 81 to 90% and 91 to 100% respectively. The average plant availability was 99%. The advantages of this process over existing processes include high plant availability, high consistency, robustness and simplicity of the operation.

Jan 1, 2004

By T. DebRoy

In recent years rapid technological advances have been achieved in the application of high energy density heat sources such as lasers and electron beams in diverse metals processing operations such as metal refining, fabrication, coating, surface modification and alloying. However, our phenomenological understanding of these new and emerging processes has not kept pace with the technological achievements. Inadequate understanding of plasma-metal interactions, the complexity of the component physical processes, and the scarcity of thermophysical data at temperatures much higher than the melting points of metals are the main difficulties in the comprehensive analysis of these processes. Several unique contemporary issues related to metals processing with high energy density beams such as rapid evaporation of alloying elements during processing and the role of plasma in influencing vaporization rate interfacial tension and species solubility in metals are discussed in this paper.

Jan 1, 1993

By Tao Zhang, Wen-tao YU, Hai-bin ZUO, Jian-Liang Zhang

Sintering-pot tests and metallurgical performances of sinter with 4 kind of different Al2O3 contents are experimented in this paper. Results show: when the Al2O3 contents increase from 2.0% to 3.5%, acicular calcium ferrites in mine phase will be gradually replaced by plate-like iron calcium. The increase of Al2O3 contents will lead to the addition of liquid viscosity and the reduction of permeability of sinter bed. Sintering time will be prolonged. The rate of yield is stable basically but production is low; besides, the increase of liquid viscosity will decrease of drum strength. The change of permeability of the material layer will make RDI +3.15 decrease first and then increase when Al2O3 contents changed from 2.0% to 3.5%. RI of sinter shows a contrary trend because many open voids are formed by deterioration of liquidity first and then pores closed.

Jan 1, 2015

By Mansoor Barati, Leili Tafaghodi Khajavi

"This study involves employing solvent refining as a purification process in which silicon recrystallization takes place from an iron-silicon melt. It is believed that iron will act as the impurity “getter” and purified silicon crystals will grow from the alloy melt, while the impurities are segregated to the liquid alloy. Phosphorous is a problematic impurity to remove since its segregation coefficient in pure silicon is relatively large. To assess the feasibility and efficiency of phosphorous removal through solvent refining, it is critical to study its equilibrium distribution between solid Si and the Fe–Si alloy phase.The distribution of phosphorous between solid silicon and iron-silicon melt at 1210-1310 °C was measured to evaluate the impurity removal potential of each alloy. Interaction parameter between phosphorous and iron was calculated by varying the concentration of phosphorous in silicon.IntroductionAmong various semiconductor materials for manufacture of solar cells, silicon accounts for over 90 percent of today's PV materials [1, 2].The major challenge in producing solar silicon that operates efficiently is to meet purity level requirement through a cost efficient route. Silicon solar cells can play a significant role in answering the world's need for energy if cost reductions can be achieved through manufacturing process. Considerable effort has been made to replace the expensive, complex vapor-phase purification by a simpler and less costly process. One of the refining approaches that have attracted wide research interests is producing low-cost solar grade silicon by purification of metallurgical grade silicon. Since metallurgical processes are selective in removing impurities, a combination of various purification processes can be used to reduce the impurity level in silicon. Considering different thermodynamic characteristics of impurities, each refining step is responsible for lowering specific impurities."

Jan 1, 2012

By H. Y. Sohn

The ignition and combustion of chalcopyrite particles under suspension-smelting conditions, in which the particle-particle interaction is neglected, has been analyzed by considering the intrinsic kinetics of oxidation and heat and mass transfer between the particle and its surroundings. Reasonable agreement has been obtained between the calculated results and experimental results from a laminar-flow furnace reported in the literature. This computation- al procedure has further been applied to flash-smelting conditions. Under suspension-smelting conditions (Sh = Nu = 2), chalcopyrite particles ignite at around 960 K. The effects of various parameters, such as oxygen concentration, particle size, and gas temperature, have also been evaluated. Comparison between calculated results in this work and experimental observations indicates that SO is the important gaseous product that forms at the surface of the particle.

Jan 1, 1993

By Kimiaki Utsunomiya, Yasumasa Hattori, Yoshiaki Mori, Toyokazu Okubo

"The effect of various operating conditions on splashing behavior in a Peirce-Smith converter has been investigated with a 1/5.7 scale cold model. Dynamic similarity between the model and a commercial converter was attained by setting the modified Froude number in the model experiments in· the range for normal converter operation. It is known that for a given modified Froude number the dimensionless penetration length of gas into the liquid phase increases as the liquid density decreases. Moreover, penetration· length has a large effect on splashing behavior. Therefore, a heavy liquid, a mixture of water and lead concentrate was used as the liquid phase. It was concluded that the amount of splash dramatically decreases with a reduction in the buoyancy energy per, unit liquid mass and an increase in the horizontal distance between the tuyere tip and the edge of the mouth.IntroductionSubmerged gas injection is widely used in practice in ferrous and nonferrous pyrometallurgical operations to achieve large gas-liquid contact areas and good agitation of liquid for rapid chemical reaction. The common application in ·nonferrous industry is the Peirce-Smith converter with multi-tuyere for copper and nickel matte converting. This process has been used for over 100 years because of its effectiveness in mixing of the molten bath, as well as its merits of the engineering simplicity. However, the mechanisms which · determine the blowing performance is poorly understood, and the design and operating conditions of the Peirce-Smith converter varies widely from plant to plant, such as by diameter, length, mouth angle, tuyere position and level of molten matte. Smelters have continuously made an effort to increase converter productivity, implying maximum tuyere blowing rate. Above a certain critical blowing rate, splash of molten matte from the converter mouth becomes unacceptable because of dangerous ejection and accretion buildup around the converter mouth, which results in interference with effective hood sealing. In fact, a 1993 converter survey[!] reported that splash was a major limiting factor for blowing rate and 54% of responding plants from around the world regard it as a limiting condition[2]. In order to increase tuyere blowing rate a study of the effect of various operating conditions on splashing behavior is expected."

Jan 1, 2000

By Mark Tsirlin

Kinetics of the initial oxidation stages of diffusive silicide coatings on 8 molybdenum and niobium at 1100 - 1700 and under the pressure of 400 and 1330 Pa has been studied using methods of gravimetry and gas phase analysis of oxygen, as well as by SEK, XRD and EDMA methods. The first oxidation stage described by asymptotic equation in case of NbSi coating changed over to the stage described by parabolic equation. The asymptotic law was shown to depend on non - stationary conditions on the oxide layer boundaries. Interconnection between silicides and quartz structures, on the one hand, and peculiarities of oxidation kinetics, on the other, is [discussed. The possibility of estimation oxygen atom jump frequency in quartz and fractions of oxygen reacting with metal and with silicon proceeding from the analysis of the kinetic data was ascertained. Conditions of oxidation kine- tics transfer from asymptotic (or parabolic) stage to a non - protective "linear" stage, associated with volatile ~roduct formation, are also discussed.

Jan 1, 1995

By J. R. Rendón

Cylinders of commercial aluminium alloy 6063 were homogenized under different conditions. The experimental results indicated that the general mechanical behaviour as related to curves of 0.2% yield strength, ultimate tensile strength and Brunnell hardness versus homogeneizing process is the same in both cases. The mechanical properties as compared to those required by plant specifications, tend to be better with increasing values of % Mg2Si in the alloy, as expected. The electron microscopy investigations revealed that in both homogeneizing processes the resulting microstructure consist of significant spheroidizing of the alpha phase (AlFeSi) and fine-needle type structure of beta phase. The alpha phase was also present in a Chinese type scripture. Furthermore, the slow cooling within the furnace resulted in the nucleation and growth of Mg2Si precipitates generally along the grain boundaries.

Jan 1, 1997

By Thomas E. Weyand

Prior to 1975, lead-based paints were commonly used in protecting steel structures. Because of the toxic effects of lead on human health and the environment, their use has been significantly reduced. However, problems with these paints persist when they are removed during normal maintenance by pneumatic blasting with mineral abrasives. Technologies are developed to contain the spent abrasive and paint during blasting operations. This paper reports on A study to identify beneficial reuses for the spent blasting material. Nine samples were gathered from different projects within Pennsylvania. The samples were thoroughly characterized with regard to composition, morphology, and EP and TCLP leach test performance. Potential reuse applications will be reviewed with regard to technical adequacy, economics, and environmental constraints.

Jan 1, 1992

By Joon H. Jang

At a selected pH, hydrothermal oxidation of chalcopyrite was carried out under controlled F+,, at elevated pressures and temperatures (172-200°C) by balancing the rate of oxygen injection against the rate of consumption. Chalcopyrite was converted to covellite (CuS) and digenite (CU1.8S) with rejection of iron and sulfur to the solution. Covellite forms in the first stage, followed by nucleation and growth of digenite in the second stage. The effects of rapid and slow injection of stoichiometric quantities of oxygen are compared. Both the covellite and digenite form a porous layer occupying the same volume as the original chalcopyrite grain. An electrochemical kinetic model is presented to correlate the observed results.

Jan 1, 1993

By Baozhong Zhao

Experimental results have shown that fluxing with soda ash (Na:zC03) can remove As and Sb from molten copper at the rate of As>Sb, but is relatively ineffective in removing Hi. The rate of impurity removal is controlled by impurity mass transfer in the metal phase. In this paper, a mathematical model was developed to describe the impurity removal phenomena. The model incorporates the effects of molten bath mixing intensity, soda ash feeding rate, oxygen content in the molten copper and soda ash fluxing by surface addition and injection. The model predictions are in good agreement with experimental results and may be used in designing large scale tests.

Jan 1, 1996

By P. Myllykoski, J. Nylander

"A commercial program package called Crownoff for the simulation of temper rolling in four high mills has been verified against measured data. The agreement between measured and calculated transversal strain distributions of the strip was found to be good. Effects of the strip crown and work roll bending force on the strain distribution were simulated. The results showed that when a single ground camber of work rolls is used for all strip widths; the strip crown should be parabolic, excluding the edge drop. An increase or decrease of the strip crown by 30 % during a coil can be compensated by a 2 to 5 t change in the work roll bending force. The ability to control the strip crown by work roll bending was insensitive to strip width. IntroductionCold rolled steel strips are usually temper rolled after recrystallization annealing, which follows cold rolling. The purpose of temper rolling is to suppress the yield point, finish the strip surface and correct possible flatness errors. The presence of a yield point might otherwise cause problems during subsequent forming processes. The in homogenous yielding in non-temper rolled steels leads to the formation of Lüders bands in the strip surface.The rolling force is influenced by the rolling speed and changes in frictional conditions in the roll bite. Therefore it is very important to plan carefully the mill settings and control algorithms during rolling. The purpose of mill control algorithms is to ensure constant reduction and the best possible strip flatness during the entire coil.Correctly predicting the rolling force is important for determining the mill presettings. Torque, forward slip and power requirements are not usually critical, if the reductions are small. However, the large elastic deformations occurring in the roll bite make the physical description of the process difficult. Physical rolling models developed for cold rolling contain assumptions that lose their validity as the reductions decrease to the level of one per cent."

Jan 1, 1994

By J. L. Jambor, H. W. Nesbitt

Oxidative dissolution of pyrrhotite and pyrite is largely responsible for the sulfate-rich waters of the vadose zone in the Waite Amulet tailings. Although the shallowest of the sulfate-rich waters are of the Fe-SO4 type, they change to Mg-SO4-type, near-neutral waters within 1-2 m of the tailings surface. Phyllosilicates and amphiboles are the only minerals present in sufficient quantity to ameliorate the amount of acidity produced. X-ray diffraction and microscopic studies of bulk sample indicate that quartz, chlorite, talc, amphiboles, magnetite, albite, and micas are the major and minor non-sulfide minerals, but their variations with depth do not give clear indications of depletion in the vadose zone. Mineralogical and bulk chemical compositions of the tailings confirm that Fe2O 3 has accumulated in large quantity in the vadose zone, with the Fe having been derived from Fe sulfides. When the effect of Fe2O3 is accounted for, the bulk compositions suggest that SiO2 is slightly more abundant in the vadose zone than in the saturated zone. This may be the result of residual enrichment of siliceous minerals such as quartz and albite in the vadose zone. Weathering of the tailings since the cessation of deposition in 1962 has resulted in a well-defined zone of sulfide depletion and secondary sulfate-mineral development. Although some silicate dissolution is indicated by pore-water compositions, the role of silicates in providing neutralization seems to have been minimal. The contribution by silicate minerals in laboratory tests of neutralization potential may be excessive relative to that in natural settings.

Jan 1, 1999

By V. J. Ramirez, A. M. E. Noguez, M. J. Navarrete, B. G. Salas, N. T. Robert

"The close die forging stress in truncated conical cavities is evaluated with dimensional analysis. Five dimensionless groups are proposed from the process variables in order to simplify the forging stress determination. These groups are experimentally related and graphically expressed. This methodology can be used to predict the actual forging stress in industrial close die forgingThe use of the dimensionless groups allow to comprise more cases than the presented here, provided similar geometries and operational conditions.Introduction.Closed die forging is essentially a plastic deformation inside a two piece mold (forging die) with the inverted shape of the actual forging geometry. This plastic deformation will always be the result of a compressive stress. There are theoretical models which include complex calculations for the analytical determination of stresses (1, 2, 3, 4). Results of these calculations are approximate, requiring generally ulterior tests to obtain the true operational conditions(5).In this paper, it is presented a simplified approach to the actual compression stress needed in the forging. A well known tool in engineering: the Buckingham's Pi theorem in conjunction with dimensionless groups and a working piece scale model is used. Dimensional analysis will give the dimensionless terms needed to experiment with a selected scale model geometry to make the stress determination. The results presented demonstrate the reliability of this methodology."

Jan 1, 1997

By B. Mishra, W. A. Averill

"The application of various hydrometallurgical, pyrometallurgical and electrochemical processes in the extraction, purification and production of radioactive metals as well as the use of various materials, ego metals and alloys, ceramics, polymers, etc. in the process, construction and handling equipment in the nuclear industry has generated a large stockpile of radioactively contaminated waste material and scrap metal which can not be directly discarded, recycled or considered for long-term storage due to its volume and potential hazards, without the separation of radionuclides. This paper reviews the emerging methods that have been investigated and suggested for dealing with some of these wastes and scrap material.The separation technologies studied for the recovery of radioactive components from the pyrometallurgical and electrochemical processing wastes have been discussed in details with results from some of the recent theoretical and physical modeling work as well as the data obtained from the actual waste treatment. Specific processes shall be described in terms of its advantages and limitations. These emerging separation technologies are being considered by the US Department of Energy as alternatives for dealing with the issues of environmental management [EM] and decontamination and decommissioning [D&D].IntroductionThe high temperature carbothermic or metallothermic smelting reduction methods for metal production are associated with the generation of significant quantity of waste as slags, flue dusts, sludges, residues, effluent salts etc. Certain hydrometallurgical processes also generate lots of aqueous waste due to the inherent nature of the technique. Also, the gas-based reduction processes are not applicable to many stable metal compounds, such as alumina, titania, beryllia, lanthanide and actinide oxides, etc. due to thermodynamic considerations. All these methods cause substantial environmental hazard. There is a need to develop alternative processes which have low waste or ideally a ""zero-waste"" generation.Pyrochemical processes using molten salts provide a unique opportunity for the extraction and refining of many reactive and valuable metals either directly from the beneficiated ore (aluminum, beryllium, neodymium, plutonium, uranium, etc.) or from other process effluent that contain reactive metal compounds. The processes reduce metal compounds electrolytically (A12O 3 and BeCI2) on a carbon anode or by calciothermic reduction (Po, Nd). The by-product, in the latter case, is a calcium oxide saturated halide salt. The waste-treatment to recycle the halide has to be done as a separate step or stored as a contaminated waste. A successful separation technology can provide a new insight to the waste minimization strategy for the nuclear industry."

Jan 1, 1996

By S. K. Wu, Ray Y. Lin, Sunil Annaji

Infrared joining of TiAI using aluminum foils as the filler material was investigated at temperatures between 1050 °C and 1350 °C in a flowing argon environment for times varying between 15 and 60 seconds. Using aluminum foils, the attempt was to form the Al3Ti phase in the joint as a result of reaction between Al and TiAI at temperatures above the melting point of Al. It has been found based on X-ray diffraction and TEM analysis that, Al3Ti, indeed is the product of infrared joining of TiAI using Al as the joining alloy. Al3 Ti was detected even in the joint processed at 1050 °C for only 15 seconds. Since the aluminum foil used in this study contains 27 at% Si, the t 2 phase in the Ti-Al-Si ternary system is believed to have also formed at the joint/base TiAI interface. Cross sectional studies on the joined specimens have shown different degrees of reaction depending on the temperature and time of joining. Micro hardness evaluations across the joint show that the hardness near the center of the joint is typically smaller than that near the joint edge next to the base material. However, as the joining temperature and time increase, the increment of the hardness at the center of the joint is faster than that around the periphery of the joint.

Jan 1, 1996